Title:X-ray Detection of the Proto Supermassive Binary Black Hole at the Centre of Abell 400

Abstract: We report the first X-ray detection of a proto-supermassive binary black hole
at the centre of Abell 400. Using the Chandra ACIS, we are able to clearly
resolve the two active galactic nuclei in 3C 75, the well known double radio
source at the centre of Abell 400. Through analysis of the new Chandra
observation of Abell 400 along with 4.5 GHz and 330 MHz VLA radio data, we will
show new evidence that the Active Galactic Nuclei in 3C 75 are a bound system.
Methods. Using the high quality X-ray data, we map the temperature, pressure,
density, and entropy of the inner regions as well as the cluster profile
properties out to ~18'. We compare features in the X-ray and radio images to
determine the interaction between the intra-cluster medium and extended radio
emission. The Chandra image shows an elongation of the cluster gas along the
northeast-southwest axis; aligned with the initial bending of 3C 75's jets.
Additionally, the temperature profile shows no cooling core, consistent with a
merging system. There is an apparent shock to the south of the core consistent
with a Mach number of M~1.4 or speed of v~1200 km s^-1. Both Active Galactic
Nuclei, at least in projection, are located in the low entropy, high density
core just north of the shock region. We find that the projected path of the
jets does not follow the intra-cluster medium surface brightness gradient as
expected if their path were due to buoyancy. We also find that both central AGN
are extended and include a thermal component. Based on this analysis, we
conclude that the Active Galactic Nuclei in 3C 75 are a bound system from a
previous merger. They are contained in a low entropy core moving through the
intra-cluster medium at 1200 km s^-1. The bending of the jets is due to the
local intra-cluster medium wind.